Semiconductor device and method of fabricating the same

A method of fabricating a semiconductor device having a first region, a second region, and a third region between the first and second regions includes forming first and second preliminary active patterns protruding from a substrate in the first and second regions, respectively, forming mask patterns exposing the third region on the substrate, performing a first etching process using the mask patterns an etch mask to form first and second active patterns, respectively, and forming gate structures on the substrate.